wolfssl: Use the return value from unit.test as pass/fail indicator

Using a string search for Fail is not going to work always e.g.
when all tests are passing it still prints a summary string with string
"Fail" in it which points to 0, however the logic here catches that and
counts it as 1 failure and marks the return value as 1 and ptest runner
interprets that as failure

Pass the return value from unit.test which should be 0 on all passes
or non zero otherwise.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-connectivity/wolfssl/files/run-ptest

@@ -8,7 +8,9 @@ echo "Wolfssl ptest logs are stored in ${temp_dir}/${log_file}"
 
 ./test/unit.test > "$temp_dir/$log_file" 2>&1  
 
-echo "Test script returned: $?"
+ret=$?
+
+echo "Test script returned: $ret"
 
 MAGIC_SENTENCE=$(grep "unit_test: Success for all configured tests." $temp_dir/$log_file)
 
@@ -21,4 +23,4 @@ else
 fi
 NUM_FAILS=$(grep -c "Failed" $temp_dir/$log_file)
 
-exit $NUM_FAILS
+exit $ret